1. Field of the Invention
This invention relates to a telephone set.
2. Description of the Related Art
Recently, a telephone set of a type, which receives data (hereunder referred to as calling phone number data) representing a telephone number (hereunder referred to as a calling phone number) of a calling subscriber sent from an exchange (namely, a central office) along with a ringing signal and displays a calling phone number indicated by the received calling phone number data, has been coming into wide use. When using a conventional telephone set of this type, a user (namely, a called party) can know from the indicated phone number who gives a call to the user (namely, who is a caller, namely, a calling subscriber), before a called phone handset becomes off-hook. Thus the user can judge whether or not he needs to respond to the call. Namely, the conventional telephone set of such a type has a merit in that it can save its user's trouble of reluctantly responding to unnecessary phone calls.
However, the conventional telephone set of such a type has drawbacks as will be described hereinbelow. Namely, in analog signals on an analog telephone line or circuit, a signal representing calling phone number data sent from a central office is inserted between intermittent ringing signals, as illustrated in FIG. 3. Therefore, a called phone rings for a moment in response to a ringing signal first sent from a central office. A ringing sound irritates and displeases a user (namely, a called party), for example, in case where he is going to concentrate his mind upon his work. If a call is given to a user by any caller to whom the user need not respond, a ring is not preferable even though the duration thereof is very short.
Even in case of employing a telephone set of the above described type which can display the phone number of a caller, a user cannot readily know who is a caller, if the user is immersed in his work at a distance from the telephone. Namely, the user cannot see the displayed phone number of the caller if he does not come up to the called phone. This is very troublesome to the user. The present invention is created to eliminate such drawbacks of the conventional telephone set.